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We have used an intensity modulated optical spectrometer, which measures the phase shift across tissue experienced by intensity modulated near-infrared light, to determine the absolute optical pathlength through tissue. The instrument is portable and takes only 5 s to record pathlength at four wavelengths (690 nm, 744 nm, 807 nm and 832 nm). The absolute(More)
Near infrared spectroscopy (NIRS) has been used to measure concentration changes of cerebral hemoglobin and cytochrome in neonates, children, and adults, to study cerebral oxygenation and hemodynamics. To derive quantitative concentration changes from measurements of light attenuation, the optical path length must be known. This is obtained by multiplying(More)
Quantitation of near infrared spectroscopic data in a scattering medium such as tissue requires knowledge of the optical pathlength in the medium. This can now be estimated directly from the time of flight of picosecond length light pulses. Monte Carlo modelling of light pulses in tissue has shown that the mean value of the time dispersed light pulse(More)
The technique of near-infra-red spectroscopy allows safe continuous monitoring of changes in blood and tissue oxygenation on an intact organ. This is made possible by observing spectral changes in the tissues caused by oxygenated haemoglobin [HbO2], deoxygenated haemoglobin [Hb] and cytochrome aa3 [Cyt aa3]. The paper describes the design and performance of(More)
We have collected multiwavelength near-infrared (NIR) attenuation spectra on human forearm muscle, the adult rat head, and newborn piglet head to compare the changes in chromophore concentration derived from these data using published algorithms from four groups. We find differences between the results from the algorithms on each data set, particularly in(More)
This paper extends our work on applying the Finite Element Method (FEM) to the propagation of light in tissue. We address herein the topics of boundary conditions and source specification for this method. We demonstrate that a variety of boundary conditions stipulated on the Radiative Transfer Equation can be implemented in a FEM approach, as well as the(More)
Near-infrared light propagation in various models of the adult head is analyzed by both time-of-flight measurements and mathematical prediction. The models consist of three- or four-layered slabs, the latter incorporating a clear cerebrospinal fluid (CSF) layer. The most sophisticated model also incorporates slots that imitate sulci on the brain surface.(More)
Current methods for measuring cerebral blood volume (CBV) in newborn infants are unsatisfactory. A new method is described in which the effect of a small change (5-10%) in arterial oxygen saturation (SaO2) on cerebral oxyhemoglobin [HbO2] and deoxyhemoglobin [Hb] concentration is observed by near-infrared (NIR) spectroscopy. Previous experiments in which(More)
Functional near infrared spectroscopy (fNIRS) is an emerging tool for non-invasively monitoring the haemodynamic response to brain activation. The technique has been widely adopted to investigate cortical responses during motor tasks in health and disease. This systematic review provides a critical analysis of the research findings in the hope of summating(More)